Procedures were developed which allowed isolation of relatively large amounts of Rauscher murine leukemia virus subunit RNA (35S). This 35S subunit RNA will be used as a messenger RNA in several different cell-free protein synthesizing systems. In another phase of this work, procedures were developed to study the biosynthesis of Rauscher leukemia viral proteins in whole cell systems. Our results show that the major structural protein of the virus, GS-1 or p30, is formed via synthesis of several high mol. wt. precursor polypeptides termed: Prla plus b (approximately 200,000 daltons), Pr3 (approximately 80,000 daltons) and Pr4 (approximatey 65,000 daltons). A second viral structural protein, p12, is made via a 90,000 dalton glycoprotein fraction termed Pr2a plus b. The research goals for the coming year are: a. To translate 35S RLV subunit RNA in cytoplasmic extracts from rabbit reticulocytes, wheat embryo, RLV-infected JLS-V5 cells, and uninfected N.I.H. Swiss mouse embryo cells. b. To determine the physical and chemical properties of the proteins made in cell-free protein synthesizing systems in response to RLV 35S subunit RNA. Techniques such as SDS-PAGE, specific immune precipitation, and tryptic mapping will be employed. c. To determine which intracellular viral precursor polypeptides (if any) contain viral proteins gp69/71, p15,p10, and the reverse transcriptase. BIBLIOGRAPHIC REFERENCES: Naso, R.B., L.J. Arcement, T.G. Wood, T.E. Saunders, and R.B. Arlinghaus: The Cell-Free Translation of Rauscher Leukemia Virus RNA into High Molecular Weight Polypeptides. Biochemica et Biophysica Acta, 282:195-206, 1975. Naso, R.B., L.J. Arcement, and R.B. Arlinghaus: Biosynthesis of Rauscher Leukemia Viral Proteins. Cell, 4:31-36, 1975.